The continuing purpose of this project is to identify animal models applicable to further research into the etiology of cancer in humans. Additionally, as cases accumulate, the probability increases that domestic pets with some types of spontaneous cancers can be identified as representing the effects of low level environmental exposure to carcinogenic agents. The frequency of cancer in these animals would serve as a warning of general environmental hazards to man. The topics of current interest include: 1) environmental influenced cancer in dogs relative to the level of industrialization in their country of residence; 2) the epidemiologic features of renal carcinoma, testicular neoplasms and urethral defects in dogs with comparison to the lesion in man; and 3) a case-control study of 1500 cases of canine mammary neoplasms to determine risk associated with age, breed, obesity, prior ovariohysterectomy and prior benign mammary neoplasia.